Current electric appliances demonstrate a tendency to have a reduced weight and a smaller size, which leads to development of lithium ion secondary batteries having a high energy density. Further, lithium ion secondary batteries are used in more various fields, and thus are desired to have improved battery characteristics.
For practical use of lithium ion secondary batteries, improvement in the storage characteristics and cycle characteristics will be more and more important. Many efforts have been made to improve the battery characteristics of lithium ion secondary batteries especially by focusing on electrolyte solutions. Some studies are given as examples in the following.
Patent Literature 1, aiming to provide a non-aqueous electrolyte secondary battery with high charge and discharge efficiency and excellent cycle characteristics, discloses an electrolyte solution that contains a lithium salt and 0.5 to 10 wt. % of a cyclic acid anhydride dissolved in a mixed non-aqueous solvent that contains a cyclic carbonate and an acyclic carbonate (70 vol % or more as a total amount in the whole amount of the solvent). Use of this electrolyte solution minimizes decomposition of the electrolyte solution contained in a non-aqueous electrolyte secondary battery that includes a graphite-based negative electrode.
Patent Literature 2, aiming to provide a non-aqueous electrolyte battery with excellent safety, high charge and discharge efficiency, and high energy density, discloses a non-aqueous electrolyte that contains at least propylene carbonate and contains 0.01 to 20 mass % of a fluoride of a cyclic carboxylic anhydride relative to the whole mass of the non-aqueous electrolyte. Use of this electrolyte suppresses decomposition of an organic solvent constituting a non-aqueous electrolyte solution and hinders oxidative decomposition of the fluoride of a cyclic carboxylic anhydride.
Patent Literature 3, aiming to ensure the reliability of a battery and improve the capacity retention ratio thereof, discloses use of an organic electrolyte solution containing a specific compound.
Patent Literature 4, aiming to improve characteristics such as the cycle characteristics and the storage characteristics, discloses use of a non-aqueous electrolyte solution that contains 0.0001 to 10 wt % of an unsaturated cyclic acid anhydride with a specific structure.